JPS60187322A - Purifying method of waste - Google Patents

Abstract

PURPOSE:To purify waste matter economically and easily by using a photocatalyst activated in accordance with light energy in a method for removing harmful substances contained in the waste matter. CONSTITUTION:The waste samples introduced from a sample inlet 51 are introduced to a reactor 31 via a circulator 52. The reactor consists of light permeable material and a photocatalyst 41 is set at the bottom part. A semiconductor such as TiO2 and ZnO and a molecular photocatalyst such as porphyrin are used as the photocatalyst. The waste introduced in the reactor is photodecomposed with the light which is emitted from a light source 61 and introduced through a lens 71 and removed and the purified substances are discharged from a sample outlet 53.

Description

[Detailed Description of the Invention] The present invention decomposes harmful substances in waste such as environmental pollutants by using light energy such as solar energy and a photocatalyst that is activated in response to the light energy. , relates to a method for purifying the above waste.

Environmental pollutants and explosive evaporative substances are found in waste materials such as waste fluids and gases discharged from various factories and exhaust gases discharged from internal combustion engines such as automobiles.

Contains harmful substances such as foul-smelling substances that have an adverse effect on the human body and the environment.

Various methods have been considered for purifying waste by decomposing and removing these harmful substances.9 For example, (1) washing waste with water, acid, oil, or chemical solution; (2) A method of adsorbing and removing harmful substances in waste using activated carbon, ion exchange resin, etc.; (3) A method of removing waste by direct combustion or catalytic combustion; (4) A method of removing harmful substances in waste through direct combustion or catalytic combustion; Ozone substance. Methods of oxidizing chlorine using sodium hypochlorite, potassium permanganate, etc. are known.

However, with these conventional purification methods, running costs such as fuel costs, electricity costs, and processing liquids during the treatment process are high.
Processing equipment and equipment also need to become more complex and larger. The pre-processing and post-processing are very troublesome and there are 9 various problems. Furthermore, the current situation is that purification methods are selected depending on the condition of the waste to be treated.

The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods.

To provide an economical and simple method for purifying waste by photochemically decomposing and removing harmful substances in waste using a photocatalyst activated in response to light energy. It is in.

That is, 1) the waste purification method of the present invention is a method for purifying waste by decomposing harmful substances in the waste; 2) placing a photocatalyst and waste to be treated in a reactor; Irradiate light into the reactor.

It is characterized by decomposing the above-mentioned harmful substances by photochemical reaction.

According to the present invention, various harmful substances in waste can be removed.

It can be decomposed and removed photochemically at room temperature, there is no need for heating operations as in the conventional technology, and inexhaustible energy such as sunlight can be used as light energy for light irradiation, A method for purifying waste at low cost can be provided.

In addition, the treatment process of the present invention involves simply placing a photocatalyst and the waste to be treated in a reactor and irradiating it with light, so the operation and equipment are very simple. 9 can be decomposed and removed regardless of the

Furthermore, the photocatalyst used in the present invention suffers less from thermal deterioration and decrease in activity due to poisoning elements and has a longer lifespan than conventional catalysts such as oxidation catalysts.

Although the mechanism of purification of harmful substances in waste according to the present invention is not clear, when the photocatalyst receives light energy of the corresponding wavelength, the waste is purified by the following mechanism. Guessed.

A photocatalyst is activated by absorbing light energy and being excited by light irradiation, thereby driving oxidation and reduction reactions. This photocatalyst has I oxidation fp :ylj(
Semiconductors called solid photocatalysts such as TiOt), f zinc oxide MZnO) and compounds called molecular photocatalysts such as p-thenium bipyridiμ complex and boμfilin are included. For example, when using an n-type semiconductor as a photocatalyst,
A mechanical diagram showing the electronic state of the semiconductor in Figure 1 (in the figure, e
- is an electron, p10 is a hole.

hJ represents light energy. ) as shown.

The semiconductor is excited by receiving light energy, and electrons and holes are formed on the semiconductor surface at the bottom of the conduction band 1.

Since it exists in the upper part of the valence band 2, it holds 99 strong reduction and oxidation energy. In this state, when harmful substances in the waste come into contact with the semiconductor surface,
It is thought that due to the strong reducing and oxidizing power of semiconductors, harmful substances are decomposed and reformed into harmless substances. In addition, even if a photocatalyst absorbs light energy, the excited electrons and holes are poorly separated and recombined.9 Even if the photocatalyst does not have strong reducing or oxidizing power, the absorbed light energy is converted into heat. It is thought that the reaction can also be enhanced by

The photocatalyst used in the present invention is produced by irradiation with light.

It accelerates the catalytic reaction, and its type is not limited. For example, titanium oxide (T102)
+ Iron oxide (Fe20m), tungsten oxide (WO
j'), tin oxide (8no1), bismuth oxide (B 1 goz), nickel oxide 7v (NiO),
Copper oxide (OuzO).

Zinc oxide (ZnO), strontium titanate (8rT
tOs), silicon oxide (8tOz) *Molybdenum sulfide (MoS2).

JJIndium phosphide (InP), gallium phosphide (G
ap).

N-type and P-type semiconductors such as indium lead (InPb).

Alternatively, the semiconductor is platinum (Pt) or rhodium (Ru).

Semiconductor solid photocatalysts supporting metals or metal oxides such as niobium (Nb), copper (Ou), tin (8n), ruthenium oxide (Rub), nickel oxide (NiO*), and μthenium (such as ruthenium bipyridyl complexes) Examples include molecular photocatalysts such as Ru) complexes, porphyrins, and chlorophylls.In the present invention, one or more of these photocatalysts are used.

In the case of solid photocatalysts, in the case of solid photocatalysts, in addition to commercially available products, high-temperature firing of metal, electrolytic oxidation, chemical vapor deposition, vacuum evaporation, coating, coprecipitation, evaporative oxidation of metal halides, etc. Prepared by etc. In the case of a single molecule photocatalyst, the catalyst may be dissolved in a solvent such as water or adsorbed onto a semiconductor to provide a sensitizing effect. In addition, components of harmful substances in the waste to be treated when dissolving a single molecule photocatalyst in a solvent.

It is desirable to adjust the concentration depending on the concentration.

The reason why a metal or metal oxide such as Pt or Run2 is supported on the semiconductor is to make the photocatalyst of the semiconductor even more active, and the supported amount of the metal or metal oxide is 001 It is preferable to carry it within a range of 20 wt%.

Even better purification activity is obtained when the amount of the catalyst is supported within the range of 0.1 to 5 wt%. Note that depending on the combination of the semiconductor and metal or metal oxide.

7 - Not limited to the above range. Also, it is better to use that method.

In the present invention, waste that can be purified includes:

There are environmental pollutants, explosive evaporative substances, foul-smelling substances, etc. that are emitted from the processes of various factories and offices, or from internal combustion engines such as automobiles. For example, hydrocarbons emitted from various processes such as internal combustion engines of automobiles, painting processes of factories or business offices, etc.
Harmful gases such as ammonia, malodorous gases such as aldehydes, cellosolves, amines, indoles, and mercaptans, as well as waste fluids containing waste oil discharged from cutting factories, etc.
Bacteria and wastewater containing harmful substances such as organic phosphorus compounds and arsenic compounds discharged from various other factories.

Waste water containing microorganisms such as yeast and mold, or hydrogen chloride,
There are waste acids such as nitric acid, waste alkalis such as hydroxide, potassium hydroxide, and dirt. Also.

The waste may be in the form of gas, liquid, or solid, and more than one type of waste may be in the form of a colloid, for example, in the form of a colloid. In addition, solid waste.

In the treatment process, it can be dissolved or suspended in a solvent such as water to make it easier to contact with the photocatalyst, or it can be treated in a gas phase system where it is suspended in the form of fine particles by pulverization etc. desirable.

The photocatalyst is placed in a reactor, stirred if necessary, and waste is introduced into the reactor in a gaseous or liquid state. At the same time, the photocatalyst is irradiated with light to decompose harmful substances in the waste through photochemical reactions.

In this case, the light energy of the light irradiation used is.

It excites the photocatalyst in the reactor to give it the ability to decompose harmful substances in waste, and it uses light energy with a wavelength corresponding to excitation of the photocatalyst, which is visible wavelength or ultraviolet wavelength. It is desirable to irradiate light with a The light energy source includes a natural light source such as sunlight, light emitted from a mercury lamp, light emitted from a filament lamp such as a halogen lamp, and short arc cannon light.

Artificial light sources such as laser beams may be mentioned. Also.

Nine artificial light sources may be used simultaneously as supplementary light sources to the solar light source.

The above light irradiation method includes a method of using a transparent reactor and irradiating the outside thereof, or a method of irradiating the outside of the reactor, or a method of placing an irradiation light source inside the reactor.
There is a method of irradiating the inside of the reactor. Furthermore, irradiation efficiency can be increased by simultaneously irradiating from both the outside and inside of the reactor. Also, a Fresnel lens to increase the intensity of light.

The light may be collected by a glass lens or the like.

Optical fibers may also transport light energy.

In addition, the transparent reactor is preferably one that allows incident light to pass through without being reflected or absorbed so that the photocatalyst is efficiently irradiated with light.9 For example, it is made of glass.

It is preferable to use a material such as quartz or plastic that is highly transparent to visible or ultraviolet wavelength light.

Further, the reactor may be of a four-part system or a flow reaction system, and a combination of a batch system and a flow reaction system may also be used.

In addition, in the case of a distribution method, either a one-time distribution method or a circulation method can be used.

The photocatalyst may be in the form of a powder, colloid, liquid, plate, etc., and is preferably fixed in the photocatalyst reactor in the form of a sonoma or by coating it on glass cloth or the like. Moreover, a plate-shaped photocatalyst can also be made into a short circuit electrode plate. When the photocatalyst is a powder, it is preferable to use one whose particle size is within the range of 1000 μm or less.

Those within this range have a large surface area and high purification efficiency. Even better purification efficiency is obtained when the particle size is within the range of 0.01 to 50 μm.

In addition, if one reaction system is a liquid phase system, suspending the photocatalyst,
In the case of a gas phase system, the photocatalyst may be suspended in the gas.

The industrial waste to be treated is preferably introduced into the reactor together with the photocatalyst in a gas phase or liquid phase reaction system. When the waste is in a gaseous state, it is preferably introduced as it is or in a liquid phase system by dissolving it in a solvent such as water, and when it is in a liquid state, it is preferably introduced into the reactor as it is.

Furthermore, if the waste is in solid form, it is best to dissolve or suspend it in a solvent such as water to make it into a liquid phase system, or to make it into fine particles by pulverization, suspend it, and introduce it through a vapor phase thread. good.

Through the above steps, harmful substances in the waste are decomposed by the photochemical reaction of the photocatalyst, and finally.

It can be removed by reforming it into harmless substances such as carbon dioxide (30g) and hydrogen (2).

Hereinafter, nine aspects of the present invention will be described in detail.

Embodiment 1 FIG. 2 shows a schematic diagram of a device for decomposing and removing harmful substances used in this embodiment. That is, a photocatalyst 41 is installed at the bottom of a reactor 31 made of glass, which is a light-transmitting material, and a waste sample is introduced through a sample inlet 51, and is introduced into two reactors via a circulator 52. ing. Light emitted from the light source 61 passes through a lens 71 and enters the υ9 reactor. It is a closed circulation system device in which the treated waste is removed through the sample outlet 53 (note the glue in Figure 9)-11
− represents light energy μ. ).

As a photocatalyst, ethyl cellosolve, which has a crystalline structure with a particle size of 0.103 to 3 μm as a main component, emits a bad odor and deteriorates the working environment, was used.

After installing the Tie catalyst 5f in powder form in the reactor 31 and purging the closed circulation system device with nitrogen gas, 10 pg of Tie-Cellosobu was injected through the sample inlet 51 and turned into vapor at room temperature. . At that time, the concentration of ethyl cellosolve was 5
It was 0 ppm. after that.

Ethyl cellosolve vapor was circulated at a circulation rate of 21/min, and the reactor 1 was irradiated with light emitted from a 500 W mercury lamp.

The steam after the above treatment is taken out from the sample outlet 53.

It was analyzed by gas chromatography. The results are shown in FIG. 3, which shows the change over time in the removal rate of ethyl cellosolve.

As is clear from FIG. 3, the removal rate of ethyl cellosolve increases as the irradiation time increases, indicating that the method of the present invention can remove the harmful substance ethyl cellosolve.

Embodiment 2 FIG. 4 shows a schematic diagram of a batch-type harmful substance decomposition and removal apparatus used in this embodiment (note that the symbol in FIG. 1 represents light energy). ) is shown. That is.

[
Waste 8 in which 42 was suspended was added. Next, a magnetic stirrer 54 is used to stir the inside of the reactor 31 using a stirring bar 55 at the same time.

1,! Light emitted from a xenon lamp 62 of 11+KW was irradiated into one reactor 32 through a lens 72.

As the hazardous substance in the waste, 50 ml of an aqueous solution (concentration 200'ppm) of acetaldehyde, which is one of the eight malodorous substances specified in the Offensive Odor Control Law, was used. Also,
As a photocatalyst, Tie powder with a particle size of 1 to 5Q71m (
+1 as a constant% source using 3g of anatase type crystal structure)
．． A 5kW xenon lamp was used.

The solution after the above treatment was taken out from the reactor, and the concentration of acetaldehyde was analyzed by gas chromatography. The results are shown in FIG. 5, which shows the change over time in the removal rate of acetaldehyde. As is clear from FIG. 5, the removal rate of acetaldehyde increases with the irradiation time, indicating that harmful substances can be removed by the method of the present invention.

Example 6 As a photocatalyst, chloroplatinic acid (nzPtCl, .6
Approximately 1 wt of platinum (Pt) was deposited by photoelectrodeposition using H, O).
% loading. The same equipment as in Example 1 was used as a device for decomposing and removing hazardous substances and hazardous substances in waste.

The above Pt-supported Tie and 1 g of the catalyst were placed in the reactor 31 in powder form, and after purging the above device with nitrogen gas, 50 μg of ethyl cellosolve was injected from the sample population 51 and turned into vapor at room temperature. The concentration of ethyl cellosolve at that time was 250
It was ppm. after that.

Ethyl cellosolve vapor was circulated at a circulation rate of 21/min, and the reactor 31 was irradiated with light emitted from a 500 W mercury lamp. The vapor after the above treatment was taken out from the sample outlet 53-15- and analyzed using a gas chromatograph.

The results showed that the removal rate of ethyl cellosolve increased with the irradiation time, and the removal rate of ethyl cellosolve increased with the method of the present invention.

It turns out that harmful substances can be removed.

[Brief explanation of the drawing]

Fig. 1 is a mechanical diagram showing the electronic state of the photocatalyst according to the present invention, Fig. 2 is a schematic explanatory diagram of the harmful substance removal device of Examples 1 and 3 of the present invention, and Fig. 4 is an example of the present invention. FIG. 2 is a schematic explanatory diagram of No. 2 harmful substance removal device. FIGS. 5 and 5 are graphs showing harmful substance removal rate curves according to the method of the present invention in Examples 1 and 2', respectively. 1... Conduction band 2... Valence band 31.32... Reactor, 41.42... Photocatalyst 51
...sample inlet, 53...sample outlet. 61... Mercury lamp light source, 62... Xenon lamp light source Applicant Toyota Central Research Institute Co., Ltd. (6 others) 16- Figure 7 Figure 2 t5i, 4, Firing position M (hr) Figure 4 b

Claims (1)

[Claims] (1) In a method for purifying waste by decomposing harmful substances in waste, a photocatalyst and waste to be treated are placed in one reactor, and light is emitted into the reactor. A method for purifying waste, which comprises irradiating the substance to decompose the harmful substance through a photochemical reaction. The photocatalyst according to claim (1) is one or more of semiconductor solid photocatalysts supporting metals or metal oxides such as, lvthenium biviridyl complexes, and molecular photocatalysts such as porphyrins. Waste purification methods. (3) The waste purification method according to claim (1), wherein the light irradiated into the reactor is light having a visible wavelength to an ultraviolet wavelength. (4) The waste purification method according to claim (1), wherein the waste is one or more of gas, liquid, and solid.